Kai Ichihara is a high school student who receives a strange email asking him if he wants to try "Slave Go," a mobile game that will enslave certain people if they are "captured" by taking a picture of them. After using the app on two people, Kai is shocked to learn they have disappeared and the game he thought was just a joke must be real. Then when his good friend Rinna Date also vanishes, he fears she has met a similar fate.

Confronted by a mysterious man named William Gotou, Kai is taken to a room where the slaves he captured are to participate in a death battle concocted by wealthy members of "Society," an exclusive, underground community. Betting is done through a currency called Delos and when one loses all their money, they will become a slave. Although he is able to win his first game, this is just the beginning, as Kai finds that Rinna has indeed become a slave, and in order to free her he must pay a fee of one hundred million Delos.

With William acting as his guide, Kai strives to capture strong slaves in order to help him liberate Rinna and release both of them from the clutches of Society's evil game.